This is followed by race (24 per cent), the Human Rights Commission Act (20 per cent), sex (19 per cent) and age (6 per cent).

Mr Innes told Fairfax Media there was "so much" for a disability commissioner to do, adding that in the absence of a full-time replacement, "I'm [still] doing the role without earning any money."

Australia also has no need for a so-called "freedom commissioner", Mr Innes said, arguing when Attorney-General George Brandis appointed Mr Wilson in late 2013, he "took the chance to fill a commission spot with a politician-in-waiting".

Disability advocates say it is critical that the commissioner with responsibility for disability was disabled themselves.

"You don't understand it unless you have it," Mr Wallace said. "You don't have credibility within the community."

Advocates also say a disability commissioner is needed as the government continues to roll out the National Disability Insurance Scheme and to deal with pressing issues in terms of transport access, education and the abuse of people with disabilities.

Labor similarly called on the government to re-appoint a full-time disability commissioner.

"The government should finally right this wrong and give people with disability the strong voice they once had at the Human Rights Commission.

"It says everything about the priorities of the Turnbull government that they have a commissioner for wind farms, but not a full-time disability discrimination commissioner," shadow attorney-general Mark Dreyfus and Labor spokeswoman for disability reform Jenny Macklin said in a statement.

Earlier on Monday, Mr Dreyfus also expressed concern that the government might delay filling the human rights commissioner position.

From 2009 to 2013 (under previous Labor governments), the human rights commissioner was taken on by the president of the commission and not as a dedicated separate role.

In the history of the commission, it has also not been unusual for commissioners to have multiple roles.

Between 2005 and 2009, Mr Innes was human rights commissioner as well as disability commissioner. But he said it was more appropriate for the role to come under the president.

"In just two years, Tim Wilson has single-handedly reshaped the human rights debate in Australia. He has restored balance to a debate which had previously been dominated by the priorities and prejudices of the left," he said in a statement.

"In carrying out his role as 'Freedom Commissioner' he reminded all Australians that freedom is the most fundamental human right of all.

Fairfax Media approached Senator Brandis for comment about a full-time disability commissioner, but he was travelling overseas.